Many existing car seats do not provide proper support for the spine. Existing bucket seats promote slouching and poor posture by the nature of their concave design. The concave bucket seat design causes excessive flexion of the spinal column, resulting in an overstretching of all of the back muscles, especially the erector spinae, trapezius, and the latissimus dorsi muscles. Prolonged overstretching of muscles often results in spasming and pain.
The convave bucket seats tend to interfere with attempts to assume and maintain an erect posture of the spine, head and neck. The shoulder blades are typically pushed forward, causing a traction force to be applied on the intrascapular musculature.
Existing vehicular seats that do attempt to support the lumbar spine often utilize a concave or "wrap around" design which, again, push the shoulder girdle complex forward and neglect to adequately support the thoracic spine. The existing split bench seats also do not adequately support the normal curves of the spine. However the present invention may be utilized on a split bench type vehicle seat by mounting two separate seat backs, of this invention, on a single bench.
In order to maintain one's eyes at a horizontal level while sitting in a slouched position, the upper cervical spine hyperextends and the cranium rotates posteriorly. This results in a shortening of the cervical paraspinal muscles and compression of vascular and neurological structures that exit the spine between the base of the cranium and the first and second cervical vertebrae, which pierce through the overlying suboccipital and cervical paraspinal muscles. This abnormal head forward posture causes muscle hyperactivity of the posterior cervical region and can eventually result in muscle tension headaches.
Many car seats have the seat back in a reclined or nonvertical position and may be adjusted to further recline. In an attempt to keep the eyes horizontal while the body is reclined, the head and neck automatically move forward and rotate posteriorly, thus increasing the stress on the cervical spine and its surrounding structures. The head rests on most existing seats are positioned anterior to the seat back, which reinforces the head forward posture and excessive spinal flexion.